1. Field of the Invention
The present invention relates to an exposure device used by an image recording device or an image reading device, and to an exposure method of the exposure device. More particularly, the present invention relates to an exposure device used by an image recording device or an image reading device, in which a light-receiving element is exposed with at least one of light scanning an original and transmitted through the original and light scanning the original and reflected at the original, and to an exposure method of the exposure device.
2. Description of the Related Art
Conventionally, in an image recording device such as a copying machine and a printer, or an image reading device such as a scanner, generally, a reflection original such as printed matter and photograph is mainly used as an original image. However, with the diversification of image information recording in recent years, an image recording device or an image reading device is put to practical use, in which, as well as the reflection original such as printed matter, a transmission original such as slide, proof, microfilm, negative film or the like can be used as the original image.
In an image recording (reading) device in which the reflection original such as printed matter is used, the original image is recorded in such a manner that light emitted from a light source is illuminated onto the reflection original and the reflected light reflected at the original and carrying an original image is imaged and exposed onto a recording material such as a photosensitive material, or the original image is read in such a manner that the reflected light is imaged onto a line sensor such as a CCD and is read photoelectrically.
On the other hand, in an image recording (reading) device in which the transmission original such as a negative film is used image recording is effected in such a manner that light emitted from the light source is made incident on the transmission original and the transmitted light transmitted through the original and carrying the original image is imaged and exposed onto the photosensitive material, or image reading is effected in such a manner that the transmitted light is imaged onto a CCD or the like.
In these devices, from the standpoint that an exposure optical system is made smaller or that a large-sized light source having a large amount of light is not required, a slit scanning/exposure device is often used in which a rod-shaped light source and a slit extending in the same direction as the light source are used to slit-scan an original in a direction perpendicular to the longitudinal direction of the slit and an image-receiving element such as a recording material and a CCD sensor is exposed with slit-shaped transmitted light or reflected light. A more detailed description of such a device is given as follows. Namely, the device is provided with a lamp unit comprising a rod-shaped light source, a light-adjusting filter for adjusting light from the light source in accordance with the color of an image recorded on an original, and a reflector which gathers light from the light source and light adjusted by the light-adjusting filter and irradiating the gathered light onto the original. As the lamp unit and a film original are moved relative to each other, the film original is scanned with light gathered by the reflector. Then, light transmitted through the film original is used as slit light to effect image recording or image reading.
However, when slit light scanned on the film original and transmitted through and/or reflected at the film original is scanned and exposed onto, for example, an intermediate transfer medium or the like, a large amount of light is illuminated onto the original and this amount of light may possibly be made greater than a proper amount of exposure required when an image recorded on the original is exposed onto the recording material. Accordingly, there is a possibility that, since the intermediate transfer medium or the like cannot be scanned and exposed with a proper amount of exposure, a proper image may not be obtained.
In view of the above-described circumstances, exposure processing of a recording material or the like has been conventionally effected in such a manner that, for example, two shading plates are disposed between the light-adjusting filter and the original and advances onto and withdraws from the optical axis of the light source so that an irradiation range of the slit light illuminated onto the recording material, CCD or the like becomes narrower. In this case, when the shading plates advance onto the optical axis, the irradiation range of the slit light is adapted to become narrower along the longitudinal direction of the irradiation range thereof. For this reason, the rate of change at which the irradiation range of the slit light illuminated onto the recording material or the like decreases with respect to a unit amount by which the shading plates move, is large. Accordingly, in order to expose the recording material or the like with a proper amount of light, it is necessary to precisely control movement of the shading plates. However, even if, for example, the shading plates are moved by a high-division pulse motor or the like, it is difficult to effect precise movement of the shading plates enough such that the recording material or the like can be exposed with a proper amount of light. As a result, there is a drawback with the conventional system in that, since it is not possible to expose the recording material or the like with the proper amount of light, optimal image recording or reading cannot be performed.
Meanwhile, there is considered another exposure processing of the recording material or the like with the proper amount of light, which is constructed in that, in place of the above-described shading plates, a filter is disposed with predetermined derivative or metal (chromium, silver, aluminum or the like) being deposited on a flat plate made of glass such that the amount of transmitted light continuously decreases from one end to the other of the filter and the filter advances onto and withdraws from the optical axis. However, there is a drawback in that the manufacturing cost of this type of filter is high and is not realistic.
Further, in the slit scanning/exposure device, various light sources such as a rod-shaped halogen lamp, a fluorescent light, and the like, are used. However, a light source generally has irregularities in the amount of light, which is so-called shading, in which an amount of light decreases from the center to an exterior of an irradiation position of the light source. In the case of a rod-shaped light source, the amount of light is usually high at a central portion thereof and it is low at each of both end portions. Accordingly, it is not possible to irradiate the original with a uniform amount of light throughout the irradiation region. For this reason, when image recording or image reading is effected by using the rod-shaped light source as it is, uneven density occurs on a recorded or read image in a longitudinal direction of a slit. As a result, correction of the irregularity in the amount of light is needed.
The correction of the irregularity in the amount of light is generally performed in such a manner that a correction filter having a light transmittance distribution opposite to the irregularity in the amount of light is disposed on an optical path and the amount of light decreases at the central portion in the longitudinal direction of the light source. Namely, the correction of the irregularity in the amount of light basically causes a decrease in the amount of light, and therefore, an exposure device in which an original or a photosensitive material, which requires a large amount of light, can be used, needs to improve the amount of light of the light source. For example, when a 35 mm-size negative film or the like is used as the original, negative films photographed by an unspecified large number of general users are often used. For this reason, a photographed condition of each original is not constant, and a large number of overexposed negative films are used as originals. Accordingly, in order to obtain prints on which proper images corresponding to each of negative-film originals in various photographed conditions are formed, a light source having a large amount of light is needed which can obtain an amount of transmitted light enough for exposure of an image-receiving element even when an overexposed and high-density negative film is used.
However, as described above, there is a drawback in that, since correction of the irregularity in the amount of light basically causes loss of the amount of light, a light source whose amount of light is large by the loss amount of light becomes necessary. Further, a general exposure device usually corresponds to various sizes of originals. For example, in an exposure device in which the above-described negative film is used as the original, various sizes of films from 35 mm-size to Brownie size are used. For this reason, it is necessary to use a rod-shaped light source having a length which corresponds to an original of the maximum size. However, the longer the rod-shaped light source becomes, the larger the difference in amount of light between the central portion of the light source and both end portions thereof, i.e., the irregularity in the amount of light, becomes. Accordingly, it is necessary to substantially reduce the amount of light at the central portion of the rod-shaped light source, but there is a drawback in that, when a small-sized original is used, the loss of the amount of light is excessively generated when a small-sized original is used.